Frequency doubling circuit arrangement



May' 20, 1958 N. F. VERSTER FREQUENCY DOUBLING CIRCUIT ARRANGEMENT Filed Aug. 29, 1955 INVENTOR mco FREDERfK vsnsraa W AGENT Unit 2,835,806 Patented May 2a, was

FREQUENCY DDUBLIN G CIRCUIT ARRANGEMENT Nico Frederick Verster, Eindhoven, Netherlands, assignor,

by mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application August 29, 1955, Serial No. 530,977

Claims priority, application Netherlands September 9, 1954 1 Claim. (Cl. 250--27) The invention relates to frequency doubling arrangements; it is an object of the invention to provide a simple and aperiodic frequency doubling circuit arrangement which can be used with advantage for comparatively high frequencies for example for frequencies up to a few mc./s.

According to the invention the circuit arrangement comprises two electron tubes each provided with a control grid and having a common cathode resistor included in the common cathode lead, which resistor forms part of the control grid circuits of both tubes and the input voltage the frequency of which is required to be doubled is supplied to the control grid of the first tube, the control grid of the second tube being connected via a positive grid bias supply to the end of the cathode resistor remote from the cathode. The anode of the second tube is connected via an anode resistor to an anode voltage supply and the anode of the first tube is connected to a tapping on the anode resistor, the output voltage being taken from the anode of the second tube; the control grids of both tubes have different positive bias voltages applied to them in a manner such that the output voltage produced at the anode of the second tube decreases both when the input voltage which is supplied to the first tube decreases and when it increases.

It the values of the components of the arrangement are properly chosen, undesirable harmonics of the input voltage are only weakly represented in the output voltage; thus, distortion of the output voltages due to undesirable harmonics is only from 1% to 2%.

An embodiment of the invention will now be described with reference by way of example, to the accompanying drawing, in which Fig. 1 shows a frequency doubling circuit arrangement in accordance with the invention, and

Fig. 2 shows a voltage diagram illustrating the operation of the circuit arrangement shown in Fig. 1.

The circuit arrangement shown in Fig. 1 comprises a double-triode tube comprising triodes 1 and 2. The cathodes of said triodes are connected to earth through a common cathode resistor 3, whilst the control grids are connected through different positive grid voltage supplies 4, 5 and grid resistors 6, 7 respectively to the end of the cathode resistor 3 remote from the cathodes which is connected to earth. Through an anode resistor 8 the anode of the triode 2 is connected to the positive terminal of an anode voltage supply 9, the anode of the triode i being connected to a tapping 10 on the anode resistor 8. The voltage of a generator 11 the frequency of which is to be doubled is supplied to the control grid of the triode 1; the frequency-doubled output voltage can be taken from output terminals 12 connected respectively to the anode of the triode 2 and to earth.

In the circuit arrangement shown, the triode 1 acts as a cathode follower so that the cathode voltage follows the control voltage. This cathode voltage is the input voltage for the triode 2 so that, when both, tubes are operative simultaneously, the voltage variations which are produced by the two tubes in the anode resistor 8 oppose each other. Since the anode resistor of triode 1 is part of the anode resistor included in the anode circuit of triode 2, the effective amplification of triode 2 considerably exceeds that of triode 1. Thus, of the voltage variations produced across the anode resistor 8 in accordance with an input voltage variation, the voltage variation which is produced by triode 2 predominates when both triodes are operative.

The voltage diagram of Fig. 2 shows the variation of the voltage V,, which is produced at the anode of the triode 2 as a function of an input voltage V, with proper choice of the grid bias voltages. With a negative or small positive value of the input voltage applied to triode 1 this triode is cut-off by the voltage which is produced across the common cathode resistor 3 by the anode current of triode 2. in this region, which is designated a in Fig. 2, the anode voltage V,, of triode 2 and consequently the output voltage are independent of the input voltage which is supplied to the first triode, i. e. they are constant.

it the input voltage of triode 1 is increased so as to assume, for example, the value V shown in Fig. 2, the triode 1 becomes operative. On further increase of the grid voltage of triode 1, across the anode resistor 8 voltage variations are produced by both triodes which oppose each other, as has been mentioned hereinbefore, the voltage variation produced by triode 2 predominating. Thus, the voltage produced at the anode of triode 2 increases in the region which is indicated by b in Figure 2.

At an input voltage which corresponds to a value V the voltage produced across the common cathode resistor 3 assumes a value such that triode 2 is cut-off. Thereupon triode It operates normally as an amplifier tube and a further increase in the input voltage causes a decrease in the output voltage, which is shown in Fig. 2 in the region designated 0.

By imparting a value V to the grid bias: of triode 1 the output voltage across terminals 12 will decrease both with increase and with decrease of the input voltage, with the result that the frequency of an input alternating voltage is doubled.

In the circuit arrangement in accordance with the invention a proper choice of the values of the components ensures that the ascending and descending slopes of the voltage diagram shown in Fig. 2 have a substantially symmetrical variation with respect to a vertical line passing through the point V and, that a sinusoidal input voltage produces a substantially sinusoidal output voltage at double frequency.

A preferred experimental embodiment of the circuit arrangement described had the following values:

1 double triode type E9OCC Anode resistor=3 1.3K ohms having a tapping at 8.8K

ohms on the supply side Cathode resistor: 1. 12K ohms Grid bias of triode 1:2.8 volts Grid bias of triode 2:0 volt.

In spite of the aperiodic nature of this circuit arrangement the distortion of the required double frequency proved to be only about 1% to 2% with a variation of the input frequency between 10 0/8. and 1.5 mc./s.

What is claimed is:

A frequency-doubling circuit comprising first and second electron tubes each having a cathode, a grid and an anode, a cathode resistor connected at an end thereof to the cathode of both of said tubes, an anode resistor having a tap thereon and connected atan end thereof to a 3 the anode of said second tube, a source of operating voltage connected between the remaining ends of said anode and cathode resistors, an unbypassed connection between said tap and the anode of said first tube whereby the entirety of said anode resistor comprises a load impedance for said second tube and only a portion of said anode resistor comprises a load impedance for said first tube, a

source of an alternating input signal connected to the grid of said first tube, and means connected to bias the grids of said tubes at different values so that the output voltage at the anode of said second tube decreases both when the input signal voltage increases and when the input signal voltage decreases.

References Cited in the file of this patent UNITED STATES PATENTS 2,230,243 Hatfcke Feb. 4, 1941 2,273,090 Crosby Feb. 17, 1942 FOREIGN PATENTS 150,806 Australia Apr. 9, 1953 

